1. Field of the Invention
The present invention relates to a solid composition of nifedipine (4-(2'-nitrophenyl)-2,6-dimethyl-3,5-dicarbomethoxy-1,4-dihydropyridine) and, more particularly, the invention relates to a novel nifedipine-containing solid composition having high bioavailability and small bulk for facilitating the administration thereof.
2. Description of the Prior Art
Nifedipine is a known material which possesses a coronary dilator activity and is useful for the treatment of so-called angina pectoris attack. Since it is difficult to foresee the occurrence of angina pectoris attack, the patient is sometimes forced to treat himself when an angina pectoris attack occurs and hence it is particularly desired that therapeutic substances of this kind used for the treatment of angina pectoris attack are pharmaceutical preparations capable of being easily administered as a matter of course and exhibiting a quick and certain effect. However, nifedipine exhibits low bioavailability by oral administration owing to the sparing solubility thereof and is liable to be decomposed by the action of light. Development of the aforesaid pharmaceutical preparations of nifedipine, therefore, has encountered great difficulty.
Hitherto, as the preparation of nifedipine for oral administration, there are known tablets, pills (U.K. Pat. No. 1,173,862), and oral-release capsules (U.S. Pat. No. 3,784,684). Among these preparations, the tablets and pills are reported to be less effective owing to the very slow absorbability (U.S. Pat. No. 3,784,684). On the other hand, the oral-release capsules are prepared by dissolving nifedipine using a solubilizing agent and filling the solution of nifedipine in a colored or shading capsule and hence exhibit their effect quickly and show good bioavailability. But since they are a liquid preparation, the forms of preparation are restricted and, in addition, the preparation step is very complicated as compared with the case of preparing solid preparations. Furthermore, since nifedipine is ordinally inferior in solubility, a large amount of solubilizers or solubilization aids is required for the preparation of such preparations for oral administration.
Therefore, the forms of these preparations inevitably become large and in case of commercially available liquid preparations (oral-release capsules), the weight of one capsule reaches 615 mg. In case of large tablets and capsules, specific forms such as ellipsoids and oblongs are employed for facilitating swallowing but even in such cases, they show resistance to swallowing if their weight is over 400 mg.